[client] egl: replace monolithic EGLTexture with modular version

The way things were handled in EGLTexture is not only very hard to
follow, but broken. This change set breaks up EGLTexture into a modular
design making it easier to implement the various versions.

Note that DMABUF is currently broken and needs to be re-implemented.

client/src/main.h

@@ -95,6 +95,7 @@ struct AppState
   void               * lgrData;
   atomic_int           lgrResize;
   LG_Lock              lgrLock;
+  bool                 useDMA;
 
   bool                 cbAvailable;
   SpiceDataType        cbType;